Class: MotionWiretap::Signal

Inherits:
Wiretap
  • Object
show all
Defined in:
lib/motion-wiretap/all/signal.rb

Overview

a Wiretap::Signal is much like a Promise in functional programming. A Signal is triggered with a new value, or it is completed, or canceled with an error event.

Instance Method Summary collapse

Methods inherited from Wiretap

#and_then, #cancel!, #combine, #dealloc, #enqueue, #filter, #map, #on_error, #queue, #reduce, #teardown, #trigger_changed, #trigger_changed_on, #trigger_completed, #trigger_completed_on, #trigger_error, #trigger_error_on

Constructor Details

#initialize(value = SINGLETON, &block) ⇒ Signal

The SINGLETON value does not trigger a ‘change’ event. It is for internal use only.



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# File 'lib/motion-wiretap/all/signal.rb', line 10

def initialize(value=SINGLETON, &block)
  super(&block)
  @value = value
end

Instance Method Details

#complete ⇒ Object 



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# File 'lib/motion-wiretap/all/signal.rb', line 41

def complete
  trigger_completed
end

#error(error = SINGLETON) ⇒ Object 



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# File 'lib/motion-wiretap/all/signal.rb', line 45

def error(error=SINGLETON)
  trigger_error(error)
end

#listen(wiretap = nil, &block) ⇒ Object

The Signal class always sends an initial value



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# File 'lib/motion-wiretap/all/signal.rb', line 50

def listen(wiretap=nil, &block)
  super
  unless @value == SINGLETON
    trigger_changed(@value)
  end
  return self
end

#next(*values) ⇒ Object

If you pass multiple values to this method, the ‘value’ will be the array of all the values, but they will be passed on to ‘trigger_changed’ using the splat operator, and so will be passed to listener blocks as individual arguments.

Example:

signal = Signal.new
signal.listen do |a, b|
  @added = a + b
end
signal.next(1, 5)    # works great, @added will be 6
signal.next([1, 5])  # this works, too, because of how args are assigned to blocks in ruby
signal.next(1)  # a will be 1 and b will be nil (error!)



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# File 'lib/motion-wiretap/all/signal.rb', line 36

def next(*values)
  raise "don't do that please" if values.include? SINGLETON
  trigger_changed(*values)
end

#value ⇒ Object 



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# File 'lib/motion-wiretap/all/signal.rb', line 15

def value
  if @value == SINGLETON
    nil
  else
    @value
  end
end